Global carbon cycle has received extensive attention,among which the river-estuary system is one of the important links connecting the carbon cycle between land and ocean.In this paper,the distribution and control fac...Global carbon cycle has received extensive attention,among which the river-estuary system is one of the important links connecting the carbon cycle between land and ocean.In this paper,the distribution and control factors of particulate organic carbon(POC)were studied by using the data of organic carbon contents and its carbon isotopic composition(δ13C)in the mainstream and estuary of Passur River in the Sundarbans area,combined with the hydrological and biological data measured by CTD.The results show that POC content ranged from 0.263 mg/L to 9.292 mg/L,and the POC content in the river section(averaged 4.129 mg/L)was significantly higher than that in the estuary area(averaged 0.858 mg/L).Two distinct stages of POC transport from land to sea in the Sundarbans area were identified.The first stage occurred in the river section,where POC distribution was mainly controlled by the dynamic process of runoff and the organic carbon was mainly terrestrial source.The second stage occurred during estuarine mixing,where the POC distribution was mainly controlled by the mixing process of seawater and freshwater.The source of POC was predominantly marine and exhibiting vertical differences.The surface and middle layers were primarily influenced by marine sources,while the bottom layer was jointly controlled by terrestrial and marine sources of organic carbon.These findings are of great significance for understanding the carbon cycle in such a large mangrove ecosystem like the Sundarbans mangrove.展开更多
Eolian dust preserved in deep-sea sediments of the North Pacific Ocean(NPO) is an important recorder of paleoclimatic and paleoenvironmental changes in the Asian inland. To better understand changes in the dust proven...Eolian dust preserved in deep-sea sediments of the North Pacific Ocean(NPO) is an important recorder of paleoclimatic and paleoenvironmental changes in the Asian inland. To better understand changes in the dust provenances, in this study diffuse reflectance spectroscopy(DRS) was used to extract the eolian signal recorded in sediments of ODP Hole 885 A recovered from the NPO. First, we systematically investigated sieving effects on the DRS data; then band positions of hematite(obtained from the second order derivative curves of the K-M remission function spectrum derived from the DRS) were used to distinguish different provenances of the eolian dust preserved in the pelagic sediments of this hole. Our results show that the sieving(38 μm) process can suppress effectively the experimental errors. Eolian signatures from Chinese Loess Plateau(CLP) sources and non-CLP-sources have been identified in the pelagic sediments of ODP Hole 885 A from the late Pliocene to the early Pleistocene. The provenance differences account for the discrepancies in the eolian records recovered from the pelagic sediments in the NPO and profiles in the CLP. Temporal changes in dust provenances are caused by the latitudinal movement of the westerly jet mainstream. The hematite DRS band position is a useful tool to distinguish the provenance of eolian components preserved in pelagic sediments.展开更多
Membrane lipids are thought to be a crucial part of the homeoviscous adaptation of archaea to extreme conditions.This article reviews the recent lipidomic studies of physiological membrane adaptations of archaea,asses...Membrane lipids are thought to be a crucial part of the homeoviscous adaptation of archaea to extreme conditions.This article reviews the recent lipidomic studies of physiological membrane adaptations of archaea,assesses the biomolecular basis of an organic paleothermometer,TEX86,and contemplates the future directions of archaeal lipidomics.The studies of extremophilic archaea have revealed that at least three different molecular mechanisms are involved in membrane adaptation of archaea:(1)regulation of the number of cyclopentane rings of caldarchaeol,(2)alteration of the diether-to-tetraether lipid ratio,and(3)variation of the proportion of saturated and unsaturated lipids.However,most of the studies have focused on a limited number of archaeal ether-linked lipids,such as glycerol dialkyl glycerol tetraethers(GDGTs),which only represent a fraction of the entire lipidome.Environmental factors such as growth temperature and pH have been most frequently reported,but biotic factors,including growth phases,nutrition,and enzymatic activities affecting the membrane lipid composition are often overlooked.Membrane lipids of mesophilic ammonia-oxidizing marine Thaumarchaeota have been applied in the reconstruction of past sea surface temperatures.However,recent culture-based physiological studies have demonstrated that non-thermal biotic factors,including dissolved oxygen,ammonia oxidation rate and the growth rate,are the main drivers of GDGT cyclization in Nitrosopumilus maritimus.Moreover,other related strains or ecotypes exhibit a markedly different set of stress adaptations.A trend is now developing to examine the whole lipid profile(lipidome)for studies of archaeal physiology and biochemistry related to lipid biosynthesis(lipidomics)to gain a better understanding of the biological mechanisms underpinning the applications of membrane lipid-based proxies in biogeochemical or ecological research.展开更多
基金The Scientific Research Foundation of the Third Institute of Oceanography,Ministry of Natural Resources under contract Nos TIO2020008 and TIO2019028the Project of Marine Protected Areas Network in China-ASEAN Countries,National Key Research and Development Programe under contract No.2017YFC1405100the National Science Foundation of China under contract No.41976050.
文摘Global carbon cycle has received extensive attention,among which the river-estuary system is one of the important links connecting the carbon cycle between land and ocean.In this paper,the distribution and control factors of particulate organic carbon(POC)were studied by using the data of organic carbon contents and its carbon isotopic composition(δ13C)in the mainstream and estuary of Passur River in the Sundarbans area,combined with the hydrological and biological data measured by CTD.The results show that POC content ranged from 0.263 mg/L to 9.292 mg/L,and the POC content in the river section(averaged 4.129 mg/L)was significantly higher than that in the estuary area(averaged 0.858 mg/L).Two distinct stages of POC transport from land to sea in the Sundarbans area were identified.The first stage occurred in the river section,where POC distribution was mainly controlled by the dynamic process of runoff and the organic carbon was mainly terrestrial source.The second stage occurred during estuarine mixing,where the POC distribution was mainly controlled by the mixing process of seawater and freshwater.The source of POC was predominantly marine and exhibiting vertical differences.The surface and middle layers were primarily influenced by marine sources,while the bottom layer was jointly controlled by terrestrial and marine sources of organic carbon.These findings are of great significance for understanding the carbon cycle in such a large mangrove ecosystem like the Sundarbans mangrove.
基金supported by the National Key R&D Program of China (2016YFA0601903)the NSFC-Shandong Joint Fund for Marine Science Research Centers (U1606401)+1 种基金National Program on Global Change and Air–Sea Interaction (GASI-GEOGE-03)the National Natural Sciences Foundation of China (41430962)
文摘Eolian dust preserved in deep-sea sediments of the North Pacific Ocean(NPO) is an important recorder of paleoclimatic and paleoenvironmental changes in the Asian inland. To better understand changes in the dust provenances, in this study diffuse reflectance spectroscopy(DRS) was used to extract the eolian signal recorded in sediments of ODP Hole 885 A recovered from the NPO. First, we systematically investigated sieving effects on the DRS data; then band positions of hematite(obtained from the second order derivative curves of the K-M remission function spectrum derived from the DRS) were used to distinguish different provenances of the eolian dust preserved in the pelagic sediments of this hole. Our results show that the sieving(38 μm) process can suppress effectively the experimental errors. Eolian signatures from Chinese Loess Plateau(CLP) sources and non-CLP-sources have been identified in the pelagic sediments of ODP Hole 885 A from the late Pliocene to the early Pleistocene. The provenance differences account for the discrepancies in the eolian records recovered from the pelagic sediments in the NPO and profiles in the CLP. Temporal changes in dust provenances are caused by the latitudinal movement of the westerly jet mainstream. The hematite DRS band position is a useful tool to distinguish the provenance of eolian components preserved in pelagic sediments.
基金supported by National Key R&D Program of China(Grant Nos.2016YFA0601101&2018YFA0605800)the National Natural Science Foundation of China(Grants Nos.91851210,41530105&41806085)+3 种基金the Key Project of Natural Science Foundation of Guangdong Province(Grants No.2018B030311016)the Shenzhen Key Laboratory of Marine Archaea Geo-Omics,Southern University of Science and Technology(Grant No.ZDSYS201802081843490)Shenzhen International Collaboration Project(Grant No.GJHZ20180928155004783)the Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology(Grant No.MGQNLM-TD201810)。
文摘Membrane lipids are thought to be a crucial part of the homeoviscous adaptation of archaea to extreme conditions.This article reviews the recent lipidomic studies of physiological membrane adaptations of archaea,assesses the biomolecular basis of an organic paleothermometer,TEX86,and contemplates the future directions of archaeal lipidomics.The studies of extremophilic archaea have revealed that at least three different molecular mechanisms are involved in membrane adaptation of archaea:(1)regulation of the number of cyclopentane rings of caldarchaeol,(2)alteration of the diether-to-tetraether lipid ratio,and(3)variation of the proportion of saturated and unsaturated lipids.However,most of the studies have focused on a limited number of archaeal ether-linked lipids,such as glycerol dialkyl glycerol tetraethers(GDGTs),which only represent a fraction of the entire lipidome.Environmental factors such as growth temperature and pH have been most frequently reported,but biotic factors,including growth phases,nutrition,and enzymatic activities affecting the membrane lipid composition are often overlooked.Membrane lipids of mesophilic ammonia-oxidizing marine Thaumarchaeota have been applied in the reconstruction of past sea surface temperatures.However,recent culture-based physiological studies have demonstrated that non-thermal biotic factors,including dissolved oxygen,ammonia oxidation rate and the growth rate,are the main drivers of GDGT cyclization in Nitrosopumilus maritimus.Moreover,other related strains or ecotypes exhibit a markedly different set of stress adaptations.A trend is now developing to examine the whole lipid profile(lipidome)for studies of archaeal physiology and biochemistry related to lipid biosynthesis(lipidomics)to gain a better understanding of the biological mechanisms underpinning the applications of membrane lipid-based proxies in biogeochemical or ecological research.
